To electrically connect to a circuit board, large-scale electronic components are commonly mounted in a socket soldered to the circuit board instead of being directly soldered to the circuit board. The socket has multiple contacts in a socket housing which contact contact pads arranged on a bottom surface of the electronic component.
A liquid crystal polymer (LCP) resin is often used for the socket housing. The LCP resin, however, has a coefficient of thermal expansion different from that of the circuit board. In modern applications, a large-scale CPU may have as many as three thousand contact pads two-dimensionally arranged with a pitch of 1 mm on the bottom surface. If the housing of the socket for such a large-scale electronic component is made of the LCP resin, the difference in coefficient of thermal expansion between the LCP resin and the circuit board may cause a soldering portion to crack or may cause the socket to warp when the socket returns to ordinary temperature after being soldered to the circuit board.
Accordingly, using the same material as the circuit board for the housing of the socket is contemplated for avoid warping for large-scale electronic components. In the housing of the socket, through-holes having inner wall surfaces plated with a conductive material are formed in order to electrically connect top and bottom surfaces of the housing. The passageways are circular holes. The contacts of the socket, however, are stamped or otherwise formed from a sheet metal. In the context of the above example, it is difficult to precisely and immovably place as many as three thousand of these contacts with a pitch of 1 mm to precisely connect with the through-holes.
Japanese Patent Application No. 2004-319630 discloses a board module in which two inserting ends of a lead terminal are inserted into respective passageways formed in a board and the inserted ends are soldered thereto. In the case of JP 2004-319630, however, a difference in dimensions or the like between the inserting ends and the passageways makes it difficult to precisely control the position of the lead terminal.